In simple terms, a retort is a closed, pressurized heater used to heat food products sealed within a container. For foods that are sealed and packaged in containers that require commercial aseptic sterilization, a number of different retort systems can be used.
During the high-temperature sterilization of food, the main target of sterilization is Helicobacter botulinum. This bacterium can produce toxins that can cause fatal harm to the human body. It is a heat-resistant anaerobic bacterium. It takes about three minutes in an environment of 121°C. It will lose biological activity in about 6 hours at 100℃. Of course, the higher the temperature, the shorter the survival time of the pathogen. After scientific testing, sterilization is more suitable at 121°C. At this time, the packaging has good heat resistance and the food tastes better. When sterilized at 121°C, the F value in the center of the food reaches 4, and Helicobacter botulinum will not be detected in the food, meeting the requirements for commercial sterility.
Types of sterilization retorts:
1. There are four types of sterilizing retorts in terms of control methods:
1. Manual control type: All valves and water pumps are manually controlled, including water addition, heating, insulation, cooling and other processes.
2. Electrical semi-automatic control type: the pressure is controlled by an electric contact pressure gauge, the temperature is controlled by a sensor (pt100) and an imported temperature controller (accuracy is ±1°C), and the cooling process is manually operated.
3. Computer semi-automatic control type: It uses PLC and text display to process the collected pressure sensor signals and temperature signals. It can store the sterilization process, has high control accuracy, and the temperature control can reach ±0.3°C.
4. Computer fully automatic control type: All processes are controlled by PLC and touch screen, and the sterilization process can be stored. The operator only needs to press the start button. After the sterilization is completed, an automatic alarm will sound, and the temperature control accuracy can reach ±0.1°C.
2. There are four types of sterilization methods:
1. Water Immersion retorts: During sterilization, all the food in the pot is soaked in hot water. In this way, the heat distribution is relatively even.
2. Steam retorts: After the food is put into the pot, water is not added first, but steam is directly added to heat up. Since cold spots will appear in the air in the pot during the sterilization process, the heat distribution in this method is not the most uniform.
3. Water spray retorts: This method uses nozzles or spray pipes to spray hot water onto the food. The sterilization process is through the nozzles installed on both sides or the top of the sterilization pot, spraying out mist-like waves. The hot water reaches the surface of the food, so it not only has a uniform temperature without dead spots, but also has rapid heating and cooling speeds. It can sterilize the products in the pot comprehensively, quickly and stably, and is especially suitable for the sterilization of soft-packaged foods.
4. Steam air retorts:This method of sterilization was introduced by France. It cleverly combines the steam type and the water spray type. A small amount of water is added into the pot to meet the cyclic spray use. The steam directly enters the country, truly achieving short-term high efficiency, energy saving and environmental protection, and is suitable for special products. of sterilization.
3. There are three types of tank structures:
1. Single tank retorts:
2. Double-layer retorts:
3. Double-pot parallel retorts:
4. There are three types of retort materials:
1. All stainless steel (304 material)
2. Semi-steel
3. Carbon steel
Principles for selecting retort machines
1. The selection is mainly based on temperature control accuracy and heat distribution uniformity. If the product requires strict temperature, especially export products, because the heat distribution is required to be very uniform, you should try to choose a computerized automatic sterilizer. The temperature control and pressure control of computer semi-automatic sterilizers are the same as those of computer fully automatic ones, but the price is 1/3 of those of computer fully automatic ones. For general requirements, you can choose an electric semi-automatic sterilizer. It is difficult to sterilize in manual sterilization pots. Temperature and pressure control are all done manually. It is difficult to control the appearance of the food, and the can (bag) swelling and breakage rates are high.
2. If the product is packaged with gas or the product appearance requirements are strict, you should choose a computerized fully automatic or computerized semi-automatic sterilizer.
3. If the product is a glass bottle or tinplate, the heating and cooling speeds must be controllable, so try not to choose a double-layer sterilization pot.
4. If you consider energy saving, you can choose a double-layer sterilization pot. Its characteristic is that the upper tank is a hot water tank and the lower tank is a treatment tank. The hot water in the upper tank is reused, which can save a lot of steam and is suitable for daily output of more than 10 tons. food production companies.
5. If the output is small or there is no boiler, you can consider using a dual-purpose electric and steam sterilizer. The principle is that steam is generated by electric heating in the upper tank and sterilized in the lower tank.
6. If the product has a high viscosity and needs to be rotated during the sterilization process, a rotary sterilizing pot should be selected.
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